COVER CROPS AND CROP ROTATION

Since a nursery crop is only as good as the soil it is grown in, it is vital that nursery fields be stabilized and reconditioned after each crop is harvested. Root balls remove significant quantities of soil from fields, including valuable top soil. Where fields are completely cleared by a harvest, erosion and further soil loss become dangers. The first priority of a nursery operator must be to prevent soil erosion. The second prior­ity is to rebuild the soil before the next crop of nursery plants is set out.

A cover crop is a rapidly growing, nonnursery crop used to stabilize the soil and prevent erosion. It may cover an entire field or only an area where insufficient nursery crops remain to hold the soil. Green manure is a crop that is rotated in the field with nursery crops. It, too, deters erosion but also improves the structure of the soil, fixes nitrogen, and adds valu­able organic matter. The deeper the roots of the cover and green manure crops, the greater their benefit to the soil. It is possible for one species or mix of species to function as both a cover crop and a green manure.

Cover crops are frequently planted in the fall after the harvest. Sometimes they are planted between the rows of nursery plants when harvesting is done over a period of several years. Cover crops are roto-

figure 21-17. Pot-in-pot production (Delmar/ Cengage Learning. Photo by Jack Ingels.)

tilled or plowed under each spring, returning organic matter to the soil. The seeding of another cover crop may then follow if the field is not planted right away.

Green manure crops are usually seeded in the spring and grown through the summer, then turned under before they develop seeds that could create weed problems for the nursery crop that is to follow. A win­ter cover crop may then be seeded to protect the soil from erosion until planting in the spring. Plants commonly used as cover crops or green manure include buckwheat, sudan grass, oats, rye, field corn, annual ryegrass, soybeans, alfalfa, clover, and hybrid sudan-sorghum grass.

Animal manures are also valuable soil conditioners and can be plowed under at the same time as cover and green manure crops. They can be obtained in quantity from nearby farms and slaughter houses.

SUMMARY______________________________________

Although the crops are often the same, field nurseries and container nurseries have different production objectives, different requirements of the production site, and different growing techniques. Field nurseries require productive natural soil whereas container nurseries can totally control their soil, often using purely artificial media as all or part of the

mix. The containers used are similar to those of the greenhouse industry but larger. They may also include wooden baskets and soft plastic bags. Nursery stock may be started from seed or as liners. Nearly all propaga­tive techniques are used in some way within the industry.

The layout of production fields is determined by the contour of the land, the amount of space available, the cultivation techniques used, and the methods or schedules of harvest.

Nursery maintenance has the potential to affect people beyond the boundaries of the nursery. There must be a reliable and plentiful source of good water. Its runoff must be controlled to ensure cleanliness before it enters a public waterway. The delivery system for supplemental irriga­tion of nursery crops may be permanent, semiportable, or portable.

Fertilization may be done with dry fertilizer or with liquid fertilizer in the irrigation system. Use of pest-free propagative stock and resistant varieties, good field hygiene, and application of chemical pesticides are all methods employed in pest control.

Two methods of labeling are commonly used. One method identifies all plants to the right and rear of the label until the next label is reached. The other method follows the direction of planting, changing the label as the cultivar changes.

The objective of nursery field pruning is to direct branching and create a fuller plant as quickly as possible. Certain plants warrant indi­vidual attention because of their potential value; others are given mini­mal attention since their profit return is less. Both top growth and root growth are pruned. Containerized plants do not require root pruning.

Use of pest-free propagative stock and resistant varieties, good field hygiene, directed use of pesticides, and an integrated pest management system that employs frequent scouting and rapid response are all mod­ern methods employed in pest control.

The nursery is usually harvested in the fall to ensure an ample sup­ply of plants in the spring when sales are greatest. Plants may be dug by hand or by machine. Containerized plants require little preparation for sale except to clean weeds from the containers, grade, and label.

After the harvest of a field nursery, the soil must be stabilized and reconditioned. Cover crops, green manure, and crop rotation are tech­niques utilized to rebuild the soil.

Containerized plants and harvested ball-and-burlap stock must be over-wintered properly. To prevent freezing of the roots and dry­ing by winds, nursery growers use techniques such as heeling-in, over-wintering houses, bordering pots, and pot-in-pot production.

ACHIEVEMENT REVIEW

A. SHORT ANSWER

Answer each of the following questions as briefly as possible.

1. Indicate whether the following are characteristic of container nurseries (C), field nurseries (F), or both (B).

f. Production soils are similar to those of a crop farm.

2. List three factors that determine the choice of plants to grow in a nursery.

3. List the three most common methods of plant propagation used by nursery growers.

4. If the production quota for a nursery plant is 8,000 plants and the grower estimates that 12 percent are likely to be unfit for sale due to the traditionally harsh winter weather, how many plants should be planted in the field?

5. Indicate whether the following statements apply best to permanent (P), semiportable (S), or portable (I) irrigation systems.

a. The main water lines are stationary and the lateral lines are portable.

b. The main water lines and the lateral lines are stationary and below ground.

c. The power source can be a PTO shaft.

d. The power source and pump are both mounted on a flatbed truck or cart.

e. The system is the most expensive to install.

f. The system is the least expensive to install.

g. The system is the most time­consuming to operate.

6. Describe the two ways that nursery crops are usually fertilized after planting.

7. Describe how weeds are controlled in field nurseries.

8. List the two methods most often used to label crops in field nurseries.

9. How do the pruning objectives for nursery plants differ from those for landscape plants?

10. Insert one or two words to complete each of the following sentences.

a. Evergreen trees are pinched back in the of the year.

b. Evergreen shrubs in the nursery are

sheared in the___________ of the year.

c. Root pruning of nursery plants is done

in the_________ of the year.

d. nursery plants do not require

root pruning.

e. Most nurseries harvest their field crops

in the_________ of the year.

f. Large soil balls are burlapped using the

technique of__________ .

g. Balled-and-burlapped plants should

be lifted and carried at the _____________ to

prevent injury to the plant.

h. ______ nursery plants require less time

to prepare for sale than field grown plants.

i. A rapidly growing nonnursery crop used to stabilize the soil of a nursery

and prevent erosion is termed a ______________

crop.

j. An alternate crop used to improve soil structure and nutrient content and increase organic matter is termed a crop.

B. TRUE/FALSE

Indicate if the following statements are true or

false.

1. All nurseries have the same planting layout.

2. Species cannot be randomly mixed in a field nursery.

3. Space efficiency is of concern to both container and field nursery growers.

4. Contour planting is a means of controlling soil erosion in field nurseries.

5. A side-by-side row planting on flat land does not permit cross-cultivation between plants.

6. All plants in a nursery planting must be harvested at the same time.

7. Different crops can be grown within the same nursery field.

8. Not all nursery aisles must be the same width.

9. Irrigation water runoff is of more concern in field nurseries than in container nurseries.

10. Where natural rainfall is frequent,

supplemental irrigation of field nurseries is usually unnecessary.

C. ESSAY

Assume that you are a nursery grower whose operation is located in Hardiness Zone 5. Deer and rabbits are abundant in the area. Snow fall is unpredictable, being light some years and heavy in others. At the close of the fall season you have the following inventory unsold:

a. 40 two-inch caliper deciduous shade trees, balled and burlapped

b. 25 large broadleaf evergreens in bushel baskets

c. 100 deciduous shrubs in containers Explain how you would plan to over-winter the plants and why you selected these methods.